Process for scarfing weld beads

ABSTRACT

A process and apparatus for scarfing a longitudinally extending weld bead on the outside surface of a welded metal tube. The process comprises peaking the tubing so that the major transverse tube axis is from about 5 to 40 percent longer than the minor transverse tube axis, followed by removal of the weld bead substantially flush with the outside surface of the tube. The process and apparatus is particuarly applicable to tubing having a wall thickness to diameter ratio of 2 1/2 percent or less and, more particularly, to copper or copper base alloy tubing. The apparatus includes means for peaking the tubing as aforenoted, the preferred means being the use of adjustable side enclosure rolls.

ilted States Patent 1191 1451 Sept. 4, 1973 PROCESS FOR SCARFING WELDBEADS [75] Inventor: Jerome M. Dupy, Wood River, 111.

[21] Appl. No.: 200,564

[52] 1.1.8. Cl.....l 29/481, 29/477, 90/24 B,

3,520,165 7/1970 Dodson 29/480 x .rimgr r iwklikhqid B azana VAttorney-Robert H. Bachman, Paul Weinstein et a1.

[5 7 ABSTRACT A process and apparatus for scarfing a longitudinallyextending weld bead on the outside surface of a welded metal tube. Theprocess comprises peaking the tubing so that the major transverse tubeaxis is from about 5 to 40 percent longer than the minor transverse tubeaxis, followed by removal of the weld bead substantially flush with theoutside surface of the tube. The process and apparatus is particuarlyapplicable to tubing having a wall thickness to diameter ratio of 2%percent or less and, more particularly, to copper or copper base alloytubing. The apparatus includes means for peaking the tubing asaforenoted, the preferred means being the use of adjustable sideenclosure rolls.

5 Claims, 8 Drawing Figures Patented Sept. 4, 1973 3,755,884

2 Sheets-Sheet l JEROME M. DUPY INVENTOR ATTORNEY Patented Sept. 4, 19732 Sheets-Sheet 2 JEROME/Vi DUPY INVENTOR 5W ATTORNEY PROCESS FORSCARFING WELD BEADS BACKGROUND OF THE INVENTION In the art of weldingmetal strip into tubing, it is known to use high frequency welding. Atypical example of a prior art apparatus and process is set out in US.Pat. No. 3,037,105, granted May 29, I962.

The welding process disclosed therein employs a forge welding techniquewherein there is a reduction in the girth of the tubing at the weldrolls. This girth reduction squeezes out the molten metal from betweenthe tube edges which are welded together forming a longitudinallyextending weld bead on the outside and inside surfaces of the tube atthe weld seam.

This invention is broadly directed to the removal of the weld bead fromthe outside surface of the tube by means of scarfing.

SUMMARY OF THE INVENTION In accordance with this invention, it has beenfound that the scarfing of the weld bead from the outside surface ofthin wall tubing cannot be performed satisfactorily by known techniqueswherein a cutting tool is urged against the tubing after it has emergedfrom the weld rolls to scarf off the weld bead. It has been found thatfor thin wall tubing, particularly tubing having a wall thickness todiameter ratio of 2% percent or less, that the pressure of the outsidediameter scarfing tool on the tube surface deforms the tube, therebyleaving a slight unscarfed ridge of weld bead on the outside surface.

In accordance with this invention, it has been found that this problemcan be substantially eliminated by first peaking the tubing, as by meansof a pair of squeeze rolls positioned before the scarfing tool. Thetubing as peaked is sufficiently strong to keep it from being deformedby the OD. scarfing tool resulting in a good clean smooth surface.

Further, the scarfing tool removes only a minimum width of scarf andadjacent surface, thereby yielding tubing having a superior surfacefinish, with the scarf removal area blending smoothly into the outsidesurface of the tube.

It is accordingly a principal object of this invention to provide aprocess and apparatus for scarfing the weld bead from the outsidesurface of a welded tube wherein the tubing is peaked prior to scarfingso that it will not be deformed under the action of the scarfing tool.

It is another object of this invention to provide a process andapparatus as above, wherein the major transverse axis of the tubingintersects the weld bead and is from percent to 40 percent longer thanthe minor transverse axis of the tubing.

It is a further object of this invention to provide a process andapparatus as above, wherein the tubing has a wall thickness to diameterratio of 2% percent or less.

It is a further object of this invention to provide a process andapparatus as above, wherein the tubing is formed of copper or a copperbase alloy.

Other objects and advantages will become apparent from the followingdescription and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic view of atypical prior art high frequency welding apparatus with which theprocess of this invention may be carried out.

FIG. 2 is a cross sectional view of an as-welded tube.

FIG. 3 is a cross sectional view of an as-welded tube after scarfing ofthe outside diameter weld bead.

FIG. 4 is a cross sectional view of the as-welded tubing at the scarfingtool station illustrating the deformation of the tubing by the scarfmgtool.

FIG. 5 is a cross sectional view of the tubing of FIG. 4 after theoutside diameter weld bead has been scarfed. 7

FIG. 6 is a cross sectional view of an as-welded tube peaked inaccordance with this invention.

FIG. 7 is a cross sectional view of an as-welded tube peaked inaccordance with this invention at the scarfing tool station.

FIG. 8 is a perspective view of a typical apparatus for peaking thewelded tubing in accordance with the process of this inven-tion.

DETAILED DESCRIPTION Referring now to the drawings and especially toFIG. 1, there is illustrated a typical welding apparatus 1 for weldingmetal strip in the form of a preformed open tube 2 into tubing. Theapparatus is adapted to weld together the opposed edges 3 and 4 whichform the longitudinal gap 5 in the open metal tubing 2.

The open tube 2 is formed in a forming mill (not shown) situated in lineimmediately preceding the apparatus l. The forming mill is ofconventional well known design. The forming mill may contain a pluralityof roll stands or dies which form metal strip into the open tube 2. Itis to be understood that other roll stands may be situated in lineimmediately following the apparatus 1 to further shape or size thetubing such as, for example, to correct out of roundness. The rollstands are generally power driven and, therefore, provide means forrapidly and longitudinally advancing the tubing. Alternatively, thismeans may be power driven weld rolls 6 as shown.

The weld rolls 6 comprise a pair of pressure rollers of known fonn whichengage the opposite sides of the tube 2 and cause the longitudinallyextending gap 5 therein to become closed substantially at a weld point 7forming a V-shaped gap 8. As the open tubing 2 advances to the weldpoint 7, the edges 3 and 4 at the gap 8 become welded together along theweld seam 9.

The edges 3 and 4 at the V-shaped gap 8 are heated by means of aninduction coil 10 or contacts. The induction coil 10 shown is a singleturn coil; however, a multiturn coil or other appropriate device couldbe substituted for the single turn coil.

The coil 10 is formed of wrought metal tubing. The coil is electricallyconnected to a source of high fre quency current, not shown. Thefrequency current is normally at least 10 kilocycles per second and,preferably, at least kilocycles per second or higher. The coil is alsoconnected to a source of cooling medium (not shown) which flows throughthe tubing to keep it from overheating.

The apparatus 1 may also include the following elements as shown inFIG. 1. An impeder I may be included to improve the efi'iciency of theinduction coil 10 by increasing the impedence of the high frequencycurrent paths around the back of the open tube 2. This reduces the flowof current around the back of the tube 2 and increases the flow ofcurrent along the tube edges 3 and 4 running from a point on the tubeedge 3 adjacent the coil 10 to the weld point 7 and back the opposingtube edge 4 to a point adjacent the coil 10. This results in moreefficient heating of the edges 3 and 4 of the open tube 2, the edgesbeing heated up to the welding temperature upon reaching the weld point7.

The impeder I may be of any suitably known construction and comprises aschroud 11 connected to a hollow supporting arm 12 as shown extendingdown through the gap 8. The actual shape of the schroud 11 shown in FIG.1 is merely schematic and it may have any suitable shape.

A source of cooling medium (not shown) such as water is connected to thehollow supporting arm 12 for flowing water into the schroud 11 and abouta core of magnetic material M which is held therein. The magneticmaterial in the core should be of an insulating nature to provide a coresubstantially free of eddy current losses. The core is preferably asintered magnetic oxide insulating material, preferably of types nowwell known which have a low loss factor and high volume resistivity. Asuitable material is marketed under the name Ferramic by General Ceramicand Steatite Corporation, the permeability thereof being substantiallygreater than unity. The cooling medium which passes through the hollowsupporting arm 12 flows within the schroud l1 and about the Ferramiccore M to cool the core and is generally discharged within the weldedtube 13.

Further, since the angle of the V-shaped gap 8 is important, a seamguide means 14 is generally included at a point in advance of theinduction coil to accurately space apart the edges of the tube 2 and,thereby, obtain the desired angle. The seam guide means may be formed ofa suitable insulating material protruding down into the gap so that theroll stand preceding that position (not shown) will cause the tube gapedges 3 and 4 to be pressed against the opposite sides of the seam guide14 whereby the edges are maintained with a uniform separation.

It is known as shown in FIG. 1 to employ a scarfing tool 15 to removethe weld bead and any upset metal from the outside surface of the tube13. The scarfing tool 15 generally comprises a tool bit whose cuttingedge 16 conforms to the contour of the outer surface of the welded tube13. The scarfing tool 15 is adjustably mounted in any suitably knownway, not shown, which permits its position relative to the tubing 13 tobe changed so that the amount of metal removal and alignment of the toolmay be adjusted.

As shown, the scarfing tool generally follows in line the weld rolls andprecedes in line the sizing or shaping roll stands not shown.

The welding apparatus just described is but one type of apparatus usefulwith the instant invention and numerous other high frequency weldingapparatus are known which could be employed in place thereof.

As shown in FIG. 2, the as-welded tubing 13 in accordance with thisinvention preferably has a flat oval cross section although it may haveany desired cross sectional shape. The weld bead 20 as shown comprises ahead portion 21 and an upset metal portion 22. The bead portion 21 isformed by the molten metal which is squeezed out from between the tubeedges 3' and 4' as the welding takes place. The upset portions 22 resultfrom the girth reduction at the weld rolls which causes the strip edges3' and 4 adjacent the weld bead 20 to be upset and deformed as shown.

In accordance with this invention, it is desired to remove the entireweld bead 20 comprising the bead 21 and upset 22 portions substantiallyflush with the outer surface 23 of the welded tube 13' as shown in FIG.3. When the wall thickness to diameter ratio is large, generally greaterthan 2% percent, the scarfing process and apparatus of the prior art asshown in FIG. 1 are adequate to obtain the desired scarfed tubing 13'shown in FIG. 3. However, when thin wall tubing 13' is scarfed byconventional means, namely, tubing having a wall thickness to diameterratio of 2% percent or less, it is subject to partial collapse under theinfluence of the scarfing tool 15 as shown in FIG. 4.

Under such conditions, only a portion of the weld bead 20 is removedleaving, as shown in FIG. 5, a portion of the bead 21 and upset 22portions remaining on the surface 23 of the tube after scarfing has beencompleted. The tubing 13' of FIG. 5 is unacceptable for furtherprocessing. In normal practice, the tubing 13' after scarfing of theoutside diameter weld bead passes through sizing and/or shaping rollstands. In order for these sizing and shaping operations to be properlyperformed, the outer surface 23 of the tube must be smooth. The presenceof a raised weld bead 20 as shown in FIG. 5 makes it impossible toproperly carry out these sizing and shaping operations.

Referring again to FIG. 4, the scarfing tool 15 cutting edge 16conforming as it does to the outside surface 23 contour of the as-weldedtube 13' cuts a wide scarfing area and when the tube is subject topartial collapse as shown therein the edges 17 of the scarfing tool 15may actually cut grooves or otherwise scratch the outer surface 23 ofthe tubing yielding an undesirable surface finish.

In accordance with this invention, the problems illustrated in FIG. 5are substantially overcome by peaking the tubing 13' prior to scarfing.By peaking it is meant that the major transverse axis 30 of the tubing13" intersects the weld bead 20. FIG. 6 shows a cross section of theas-welded tubing 13" after peaking in accordance with this invention butprior to scarfing. The major transverse axis 30 of the tubing 13" whichintersects the weld bead should be from about 5 to 40 percent longerthan the minor transverse axis 31 of the tubing and, more preferably,the major transverse axis 30 is from 20 to 30 percent longer than theminor transverse axis 31 of the tubing 13.

As shown in FIG. 7, the peaked tubing 13" in accordance with thisinvention is not subject to partial collapse even when the thickness todiameter ratio of the tubing is 2% percent or less. Further, as shown inFIG. 7, the cutting edge 16 of the scarfing tool 15 is shaped to conformto the surface of the tubing 13" after sizing and shaping, for example,for circular tubing it would have a circular shape. In consequence,therefore, a very narrow scarf removal area A is produced because thepeaked tube 13" contacts only a narrow portion of the scarfing tool 15cutting edge. This provides improved surface finish in the final tubing.

FIG. 8 shows a typical apparatus 40 for carrying out this invention. Theapparatus is shown in line following the weld rolls 6. It comprisesmeans 41 for peaking the tubing 13" and means 42 for scarfing the weldbead 20 from the outside surface 23 of the tubing. The peaking means 41shown in FIG. 8 comprises a pair of adjustable side enclosure rolls 43.The spacing between the rolls 43 may be adjusted by means of a crank 44.The

narrower the spacing the greater is the amount of peaking. The peakingmeans 41 shown is merely exemplary and other means for accomplishing thepeaking could be employed such as,.for example, the use of dies or thelike.

The scarfmg means 42 shown comprises a scari'mg tool adjustably held byconventional means, not shown, which do not form a part of the inventionherein. It is preferred, however, in accordance with this invention thatthe cutting edge 16 of the scarfing tool 15 has a radius whichsubstantially corresponds to the radius of the tubing after shaping andsizing for circular tubing and for noncircular tubing that the cuttingedge conform to the surface contour of the tubing.

While this invention is broadly applicable to all types of welded metaltube, it is preferred for use with cooper and copper base alloy weldedtubing with which the problem of collapseunder the action of thescarfing tool is greatest.

This invention may be embodied in other forms or carried out in otherways without departing fr0m the spirit or essential characteristicsthereof. The present embodiment is therefore to be considered as in allrespects illustrative and not restrictive, the scope of the all changeswhich come within the meaning and range of equivalency are intended tobe embraced therein.

What is claimed is:

1. A process for scarfing a longitudinally extending weld bead on theoutside surface of welded metal tubing which prevents collapse of thetubing in the area of the weld head which comprises:

peaking said tubing such that the major transverse tube axis whichintersects the weld bead is from about 5 to 40 percentlonger than theminor transverse tube axis;

removing said weld bead substantially flush with the outside surface ofsaid tube; and shaping the resultant tube to a circular configuration.

2. A process as in claim 1 wherein the tubing has a was welded by highfrequency induction welding.

l I i l l

1. A process for scarfing a longitudinally extending weld bead on theoutside surface of welded metal tubing which prevents collapse of thetubing in the area of the weld bead which comprises: peaking said tubingsuch that the major transverse tube axis which intersects the weld beadis from about 5 to 40 percent longer than the minor transverse tubeaxis; removing said weld bead substantially flush with the outsidesurface of said tube; and shaping the resultant tube to a circularconfiguration.
 2. A process as in claim 1 wherein the tubing has a wallthickness to diameter ratio of 2 1/2 percent or less.
 3. A process as inclaim 2 wherein said major tube axis is from about 20 to 30 percentlonger than said minor tube axis.
 4. A process as in claim 3 whereinsaid welded tube is formed of copper or a copper base alloy.
 5. Aprocess as in claim 4 wherein said welded tube was welded by highfrequency induction welding.